Fix 6f6f099: Signals exist only on plain rail tiles (#11977)

src/rail_gui.cpp

@@ -241,7 +241,7 @@ static void GenericPlaceSignals(TileIndex tile)
 		Command<CMD_REMOVE_SINGLE_SIGNAL>::Post(STR_ERROR_CAN_T_REMOVE_SIGNALS_FROM, CcPlaySound_CONSTRUCTION_RAIL, tile, track);
 	} else {
 		/* Which signals should we cycle through? */
-		bool tile_has_signal = IsValidTrack(track) && HasSignalOnTrack(tile, track);
+		bool tile_has_signal = IsPlainRailTile(tile) && IsValidTrack(track) && HasSignalOnTrack(tile, track);
 		SignalType cur_signal_on_tile = tile_has_signal ? GetSignalType(tile, track) : _cur_signal_type;
 		SignalType cycle_start;
 		SignalType cycle_end;